Relationships between Electrolyte Concentration and the Supercapacitive Swing Adsorption of CO2

Scaling Supercapacitive Swing Adsorption of CO2 Using Bipolar Electrode Stacks

Supercapacitive swing adsorption (SSA) modules with bipolar stacks having 2, 4, 8, and 12 electrode pairs made from BPL 4 × 6 activated carbon are constructed and tested for carbon dioxide capture applications. Tests are performed with simulated flue gas (15%CO2 /85%N2) at 2, 4, 8, and 12 V, respectively. Reversible adsorption with sorption capacities (≈58 mmol kg-1) and adsorption rates (≈38 µmol kg-1 s-1) are measured for all stacks. The productivity scales with the number of cells in the module, and increases from 70 to 390 mmol h-1 m-2. The energy efficiency and energy consumption improve with increasing number of bipolar electrodes from 67% to 84%, and 142 to 60 kJ mol-1, respectively. Overall, the results show that SSA modules with bipolar electrodes can be scaled without reducing the adsorptive performance, and with improvement of energetic performance.

Carboxysome-Inspired Electrocatalysis using Enzymes for the Reduction of CO2 at Low Concentrations

The electrolysis of dilute CO2 streams suffers from low concentrations of dissolved substrate and its rapid depletion at the electrolyte-electrocatalyst interface. These limitations require first energy-intensive CO2 capture and concentration, before electrolyzers can achieve acceptable performances. For direct electrocatalytic CO2 reduction from low-concentration sources, we introduce a strategy that mimics the carboxysome in cyanobacteria by utilizing microcompartments with nanoconfined enzymes in a porous electrode. A carbonic anhydrase accelerates CO2 hydration kinetics and minimizes substrate depletion by making all dissolved carbon available for utilization, while a highly efficient formate dehydrogenase reduces CO2 cleanly to formate; down to even atmospheric concentrations of CO2 . This bio-inspired concept demonstrates that the carboxysome provides a viable blueprint for the reduction of low-concentration CO2 streams to chemicals by using all forms of dissolved carbon.

High-Voltage Supercapacitive Swing Adsorption of Carbon Dioxide

Supercapacitive swing adsorption (SSA) with garlic roots-derived activated carbon achieves a record adsorption capacity of 312 mmol kg^-1 at a low energy consumption of 72 kJ mol^-1 and high mass loadings (>30 mg cm^-2 ) at 1.0 V for 85%N₂ /15%CO₂ mixtures. The activated carbons are inexpensively prepared in a one-step process using potassium carbonate, and air as activators. The adsorption capacity further increases with increasing voltage. At a voltage of 1.4 V, a sorption capacity of 524 mmol kg^-1 at an energy consumption of 130 kJ mol^-1 can be achieved. The volumetric sorption capacity is also enhanced and reaches values of 85.7 mol m^-3 at 1.0 V, and 126 mol m^-3 at 1.4 V. Cycle stability for at least 130 h is demonstrated.

Enhancing the capacity of supercapacitive swing adsorption CO2 capture by tuning charging protocols

Supercapacitive swing adsorption (SSA) is a recently discovered electrochemically driven CO₂ capture technology that promises significant efficiency improvements over traditional methods. A limitation of this approach is the relatively low CO₂ adsorption capacity, and the underlying molecular mechanisms of SSA remain poorly understood, hindering optimization. Here we present a new device architecture for simultaneous electrochemical and gas-adsorption measurements, and use it to investigate the effects of charging protocols on SSA performance. We show that altering the voltage applied to charge the SSA device can significantly improve performance. Charging the gas-exposed electrode positively rather than negatively increases CO₂ adsorption capacity and causes CO₂ desorption rather than adsorption with charging. We also show that switching the voltage between positive and negative values further increases CO₂ capacity. Previously proposed mechanisms of the SSA effect fail to explain these phenomena, so we present a new mechanism based on movement of CO₂-derived species into and out of electrode micropores. Overall, this work advances our knowledge of electrochemical CO₂ adsorption by supercapacitors, potentially leading to devices with increased uptake capacity and efficiency.

Electrochemical carbon capture processes for mitigation of CO2 emissions

This review discusses the emerging science and research progress underlying electrochemical processes for carbon capture for mitigation of CO2 emissions, and assesses their current maturity and trajectory.